The patch titled
Subject: kmod: don't run async usermode helper as a child of kworker thread
has been added to the -mm tree. Its filename is
kmod-dont-run-async-usermode-helper-as-a-child-of-kworker-thread.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kmod-dont-run-async-usermode-helper-as-a-child-of-kworker-thread.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kmod-dont-run-async-usermode-helper-as-a-child-of-kworker-thread.patch
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From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: kmod: don't run async usermode helper as a child of kworker thread
call_usermodehelper_exec_sync() does fork() + wait() with "unignored"
SIGCHLD. What we have missed is that this worker thread can have other
children previously forked by call_usermodehelper_exec_work() without
UMH_WAIT_PROC. If such a child exits in between it becomes a zombie
because auto-reaping only works if SIGCHLD is ignored, and nobody can reap
it (unless/until this worker thread exits too).
Change the !UMH_WAIT_PROC case to use CLONE_PARENT.
Note: this is only first step. All PF_KTHREAD tasks, even created by
kernel_thread() should have ->parent == kthreadd by default.
Fixes: bb304a5c6fc63d8506c ("kmod: handle UMH_WAIT_PROC from system unbound workqueue")
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/kmod.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff -puN kernel/kmod.c~kmod-dont-run-async-usermode-helper-as-a-child-of-kworker-thread kernel/kmod.c
--- a/kernel/kmod.c~kmod-dont-run-async-usermode-helper-as-a-child-of-kworker-thread
+++ a/kernel/kmod.c
@@ -327,9 +327,13 @@ static void call_usermodehelper_exec_wor
call_usermodehelper_exec_sync(sub_info);
} else {
pid_t pid;
-
+ /*
+ * Use CLONE_PARENT to reparent it to kthreadd; we do not
+ * want to pollute current->children, and we need a parent
+ * that always ignores SIGCHLD to ensure auto-reaping.
+ */
pid = kernel_thread(call_usermodehelper_exec_async, sub_info,
- SIGCHLD);
+ CLONE_PARENT | SIGCHLD);
if (pid < 0) {
sub_info->retval = pid;
umh_complete(sub_info);
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
kmod-dont-run-async-usermode-helper-as-a-child-of-kworker-thread.patch
mmoom-fix-potentially-killing-unrelated-process-fix.patch
mm-fix-the-racy-mm-locked_vm-change-in.patch
mm-add-the-struct-mm_struct-mm-local-into.patch
mm-oom_kill-remove-the-wrong-fatal_signal_pending-check-in-oom_kill_process.patch
mm-oom_kill-cleanup-the-kill-sharing-same-memory-loop.patch
mm-oom_kill-fix-the-wrong-task-mm-==-mm-checks-in-oom_kill_process.patch
change-current_is_single_threaded-to-use-for_each_thread.patch
signals-kill-block_all_signals-and-unblock_all_signals.patch
signal-turn-dequeue_signal_lock-into-kernel_dequeue_signal.patch
signal-introduce-kernel_signal_stop-to-fix-jffs2_garbage_collect_thread.patch
signal-remove-jffs2_garbage_collect_thread-allow_signalsigcont.patch
coredump-ensure-all-coredumping-tasks-have-signal_group_coredump.patch
coredump-change-zap_threads-and-zap_process-to-use-for_each_thread.patch
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